System and method for controlling the operation of a fuel processsing system

ABSTRACT

A control system and method for a fuel processing system. The control system automates the operation of a fuel processing system by monitoring operating parameters and automatically controlling the operation of the system responsive to the monitored parameters, predefined subroutines and/or user inputs.

RELATED APPLICATIONS

This application is a continuation patent application claiming priorityto U.S. patent application Ser. No. 10/967,696, which was filed on Oct.15, 2004 and issued on Apr. 24, 2007, as U.S. Pat. No. 7,208,241, andwhich is a continuation of U.S. patent application Ser. No. 10/138,004,which was filed on May 3, 2002 and issued on Nov. 2, 2004, as U.S. Pat.No. 6,811,908, and which is a continuation of U.S. patent applicationSer. No. 09/414,049, which was filed on Oct. 6, 1999, and issued on May7, 2002 as U.S. Pat. No. 6,383,670. The complete disclosure of theabove-identified patent applications are hereby incorporated byreference for all purposes.

FIELD OF THE INVENTION

The present invention relates generally to fuel processing systems, andmore particularly to a control system that automates the operation of afuel processing system.

BACKGROUND AND SUMMARY OF THE INVENTION

Fuel processors are used to produce hydrogen gas from a feedstock. Inrecent years, more and more research is being conducted to develop acommercially practicable fuel processor. For example, one goal is tocouple a fuel processor with a fuel cell stack to provide a fuelprocessing system that may be used as an alternative, or supplement, toconventional energy systems.

An important step to achieving a fuel processor for commercialapplications, and especially for smaller scale consumer applications, isa control system that automates at least a substantial portion of theoperation of the fuel processing system. In laboratory environmentswhere the fuel processing system is not being used continuously or leftunattended for prolonged periods of time, a manually operated system maybe acceptable. Should a problem arise, trained technicians will be onhand. However, in commercial applications, such as in households,vehicles and the like where the consumer will generally not be trainedin the operation and design of the fuel processing system, the operationof the system must be automated. Even when the fuel processing system isfunctioning properly, consumers will neither have the technicalknowledge, nor the desire, to manually control the operation of thesystem.

Therefore, there is a need for a control system adapted to automate theoperation of a fuel processor, such as a fuel processor forming aportion of a fuel processing system including a fuel cell stack. Thepresent invention provides such a control system and a method formonitoring and/or controlling the operation of a fuel processing system.

Many other features of the present invention will become manifest tothose versed in the art upon making reference to the detaileddescription which follows and the accompanying sheets of drawings inwhich preferred embodiments incorporating the principles of thisinvention are disclosed as illustrative examples only.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a fuel processing system according to thepresent invention, including a fuel processing assembly and a fuel cellstack.

FIG. 2 is a schematic view showing components of the fuel processor ofFIG. 1.

FIG. 3 is a schematic view showing the controller and the feed assemblyof FIG. 2.

FIG. 4 is a schematic view showing the controller and thehydrogen-producing region of FIG. 2.

FIG. 5 is a schematic view showing an embodiment of thehydrogen-producing region of FIG. 2 including a preheating assembly.

FIG. 6 is a schematic view showing another embodiment of the preheatingassembly of FIG. 5.

FIG. 7 is a schematic view showing the controller and the separationregion of FIG. 2.

FIG. 8 is a schematic view showing the controller, polishing region andthe output assembly of FIG. 2.

FIG. 9 is a schematic view showing the controller and the combustionregion of FIG. 2.

FIG. 10 is a front elevation view of a user interface for a controllerfor the fuel processor of FIG. 1.

FIG. 11 is a flow chart illustrating the relationships between theautomated operating states of the fuel processing system of FIG. 1.

FIG. 12 is a flow chart illustrating the relationships between thesubroutines executable by the controller of FIG. 1.

DETAILED DESCRIPTION AND BEST MODE OF THE INVENTION

A fuel processing system is shown in FIG. 1 and generally indicated at10. As shown, system 10 includes a fuel processing assembly 12 and afuel cell stack 14. Fuel processing assembly 12 includes a fuelprocessor 16 that produces hydrogen gas from a feed stream 20, whichtypically comprises an alcohol or hydrocarbon, and which may includewater. Fuel processing assembly 12 further includes a feed assembly 18that delivers feed stream 20 to fuel processor 16. Examples of suitablefeedstocks include alcohols, such as methanol, ethanol, ethylene glycoland propylene glycol, and hydrocarbons, such as methane, propane andtransportation fuels, such as gasoline, diesel and jet fuel. It iswithin the scope of the present invention that any other suitablefeedstock may be used, as is known in the art.

Fuel processor 16 converts the feedstock into hydrogen gas, at least asignificant portion of which is typically delivered to fuel cell stack14. Stack 14 uses the hydrogen gas to produce an electric current thatmay be used to meet the electrical load supplied by an associatedelectrical device 22, such as a vehicle, boat, generator, household,etc. It should be understood that device 22 is schematically illustratedin the Figures and is meant to represent one or more devices adapted toreceive electric current from the fuel processing system responsive toan applied electric load.

Fuel cell stack 14 includes one or more fuel cells adapted to produce anelectric current from the hydrogen gas produced by the fuel processor.An example of a suitable fuel cell is a proton exchange membrane (PEM)fuel cell, in which hydrogen gas is catalytically dissociated in thefuel cell's anode chamber into a pair of protons and electrons. Theliberated protons are drawn through an electrolytic membrane into thefuel cell's cathode chamber. The electrons cannot pass through themembrane and instead must travel through an external circuit to reachthe cathode chamber. The net flow of electrons from the anode to thecathode chambers produces an electric current, which can be used to meetthe electrical load being applied by device 22. In the cathode chamber,the protons and electrons react with oxygen to form water and heat.Other types of fuel cells may be used in stack 14, such as alkaline fuelcells.

Also shown in FIG. 1 is a control system 26 with a controller 28 that isadapted to automate the operation of fuel processing assembly 12, and insome embodiments, the entire fuel processing system 10. Unlikeconventional fuel processing systems, which are manually operated andrequire a trained technician to be available should the systemmalfunction or require adjustment, the performance of system 10 isregulated and automatically adjusted responsive to changes in operatingparameters detected by control system 26. As discussed in more detailsubsequently, control system 26 includes controller 28, which ispreferably software operating on a processor. However, it is within thescope of the present invention that controller 28 may be otherwiseimplemented, such as with one or more digital and/or analog circuits, orthe combination of the two.

Control system 26 further includes a plurality of sensor assemblies incommunication with controller 28 and adapted to monitor selectedoperating parameters of the fuel processing system. Responsive to inputsignals from the sensor assemblies, user commands from a user-inputdevice, and/or programmed subroutines and command sequences, thecontroller regulates the operation of the fuel processing system. Morespecifically, controller 28 communicates with a control-signal receivingportion of the desired region or element of the fuel processing systemby sending command signals thereto directing a particular response. Forexample, controller 28 may send control signals to pumps to control thespeed of the pumps, to valve assemblies to control the relative flowratetherethrough, to pressure regulators to control the pressure of theconduit or vessel regulated thereby, etc.

It should be understood that the sensor assemblies, control-signalreceiving devices, and communication pathways described herein may be ofany suitable construction known in the art. The sensor assemblies mayinclude any suitable sensor for the operating parameter being monitored.For example, flow rates may be monitored with any suitable flow meter,pressures may be monitored with any suitable pressure-sensing orpressure-regulating device, etc. The assemblies may also, but do notnecessarily include a transducer in communication with the controller.The communication pathways may be of any suitable form known in the art,including radio frequency, wired electrical signals, wireless signals,optical signals, etc.

In the Figures, communication pathways are schematically illustrated assingle- or double-headed arrows. An arrow terminating at controller 28schematically represents an input signal, such as the value of ameasured operating parameter, being communicated to controller 28. Anarrow extending from controller 28 schematically represents a controlsignal sent by controller 28 to direct a responsive action from thedevice at which the arrow terminates. For example, in FIG. 2,dual-headed pathways 62 schematically illustrate that controller 28 notonly sends command signals to corresponding receivers in fuel processor16 and feed assembly 18 to provide a determined responsive action, butalso receives inputs from sensor assemblies contained within the fuelprocessor and feed assembly.

In FIG. 2, an embodiment of a fuel processing system 10 according to thepresent invention is shown in more detail. As discussed, assembly 12 isshown schematically as an example of a suitable fuel processor and feedassembly, and other fuel processors and feed assemblies may be usedwithout departing from the spirit and scope of the present invention. Toprovide a framework for discussing the interaction of control system 26with the fuel processing system shown in FIG. 2, the principal regionsof fuel processing assembly will be briefly discussed in the followingdescription, followed by a more detailed description of each region withan emphasis on how the elements in the region interact with the controlsystem of the present invention.

As discussed, fuel processing assembly 12 includes a fuel processor 16and a feed assembly 18. Feed assembly 18 delivers feed stream 20 to ahydrogen-producing region 34 of fuel processor 16. Hydrogen-producingregion 34 produces hydrogen gas from feed stream 20 through any suitablemechanism. Suitable mechanisms include steam reforming of an alcohol orhydrocarbon vapor, partial oxidation of a hydrocarbon or alcohol vapor,a combination of partial oxidation and steam reforming a hydrocarbon oran alcohol vapor, pyrolysis of a hydrocarbon or alcohol vapor, orautothermal reforming of an alcohol or hydrocarbon. Examples of suitablesteam reformers are disclosed in U.S. Pat. No. 6,376,113, the disclosureof which is hereby incorporated by reference. When hydrogen-producingregion 34 operates by steam reforming, feed stream 20 will typicallyinclude steam and an alcohol or hydrocarbon vapor. When region 34operates by pyrolysis or partial oxidation, stream 20 will not include awater component.

From hydrogen-producing region 34, a resultant stream 36 delivers thehydrogen-containing fluid to a separation region 38. Whenhydrogen-producing region 34 is a stream reforming region, stream 36 maybe referred to as a reformate stream. In separation region 38, thestream is divided into a product stream 40 and a byproduct stream 42.Product stream 40 includes at least a substantial portion of hydrogengas and preferably contains less than determined minimum concentrationsof compositions that would damage or interfere with the intended use ofthe product stream. Ideally, stream 40 is free from such compositions,however, it is sufficient that any potentially interfering or damagingcompositions are present in concentrations that are not high enough toimpair or interfere with the intended use of stream 40. For example,when the product stream is to be delivered to fuel cell stack 14 (eitherdirectly, or after being stored for a selected period of time), thestream should be at least substantially free of carbon monoxide.However, the stream may contain water without damaging fuel cell stack14 or the production of an electric current therein.

Sometimes, it may be desirable to pass product stream 40 through apolishing region 44 in which the concentration of undesirablecompositions is reduced or removed. It should be understood thatpolishing region 44 is not essential to all embodiments of theinvention. For example, separation region 38 may result in productstream 40 being sufficiently free of undesired compositions for theintended use of the product stream.

From polishing region 44, the product stream is delivered to an outputassembly 50 from which the stream leaves the fuel processor 16 and isdelivered to a suitable destination or storage device. For example, theproduct hydrogen may be delivered to fuel cell stack 14 via stream 52 toproduce an electric current therefrom. Some or all of the producedhydrogen may alternatively be delivered via stream 54 to a storagedevice 56. Examples of suitable devices include storage tanks, carbonabsorbents such as carbon nanotubes, and hydride beds, although anyother suitable device for storing hydrogen gas may be used and is withinthe scope of the present invention.

At least portions of fuel processor 16 typically operate at an elevatedtemperature. For example, hydrogen-producing region 34 typicallyoperates at an elevated temperature, and separation region 38 mayoperate at an elevated temperature. When an elevated temperature isdesired, fuel processor 16 may further include a combustion region 60 orother suitable region for generating sufficient heat to maintain thefuel processor within selected temperature ranges.

Also shown in FIG. 2 is a user interface 58. User interface 58 enablesusers to communicate with controller 28, such as by inputting userinputs, and/or by receiving information displayed by the controller.

As shown in FIG. 2, controller 28 communicates, via one- or two-waycommunication pathways 62, with some or all of the regions of the fuelprocessing assembly described above. It should be understood that it isnot required that controller 28 communicate with each of the regions ofthe fuel processing assembly shown in FIG. 2, and that controller 28 mayalso communicate with regions other than those shown in FIG. 2. Toillustrate this point, no communication pathways 62 have been showncommunicating with polishing region 44. However, it is within the scopeof the present invention that system 26 may include one or more pathwayscommunicating with this portion of the fuel processing system.

Turning now to FIGS. 3-10, a more detailed discussion of the componentsof fuel processing system 10 is provided, including examples ofoperating parameters that may be monitored by the control system andcommand signals that may be sent responsive thereto.

In FIG. 3, an illustrative embodiment of feed assembly 18 is shown inmore detail. As shown, assembly 18 includes a pump assembly 70 thatincludes one or more pumps 72 adapted to draw flows 74 and 76 from afeedstock supply 78 and a water supply 80. When the feedstock ismiscible in water, the feedstock and water may be mixed to form acomposite feed stream 20, as shown in solid lines in FIG. 3. It iswithin the scope of the present invention, however, that the streams maybe separately delivered to fuel processor 16, as shown in dashed linesin FIG. 3. It is also within the scope of the present invention thatwater supply 80 and feedstock supply 78 include fluid connections tosources external feed assembly 18. As discussed previously, someembodiments of system 10 utilize a hydrogen-producing mechanism thatdoes not require water. In these embodiments, feed assembly 18 will notneed to include a water supply.

As shown in FIG. 3, controller 28 communicates with stream 20 to monitorand/or regulate the flowrate and pressure in the stream. When the flowsare separately drawn from their respective supplies, pump assembly 70preferably includes flow controls adapted to regulate the relative flowrate of each component of the feed stream responsive to inputs fromcontroller 28. Preferably, controller 28 also receives inputs from pumpassembly 70, such as the speed of each pump in pump assembly 70 and theflowrate of fluid in feed stream(s) 20.

Controller 28 may also receive inputs regarding the level of fluid ineach supply 78 and 80. If the level drops below a selected level, thecontroller may direct additional fluid to be added to the supply, suchas from an external source (not shown). If no additional fluid isavailable and the level drops below determined minimum levels, then thecontroller may take the appropriate programmed response, such asexecuting the control system's shutdown subroutine and alerting the userof the problem, or fault, via user interface 58. As discussed in moredetail subsequently, when the controller determines that an operatingparameter of the fuel processing system exceeds a determined thresholdvalue or range of values, it will automatically actuate a shutdownsubroutine to prevent damage to the fuel processing system.

By monitoring process parameters such as those discussed above,controller 28 may compare the measured values to expected, or stored,values to determine if the fuel processing system is operating properly.Similarly, the measured values may be used by the controller todetermine if other elements of the fuel processing system are withinacceptable operating conditions. For example, if the measured flowrate(communicated via pathway 62 and measured, for example, by any suitableflow meter) in stream(s) 20 does not correspond with the expectedflowrate, as determined by controller 28 (such as based on programmeddata, the measured pump speed, etc.), then the controller mayautomatically execute its shutdown subroutine or signal the user thatthe system requires servicing or maintenance of pump assembly 70.

In FIG. 4, feed stream 20 is delivered to hydrogen-producing region 34.Region 34 includes suitable catalysts or other structure for theimplemented mechanism by which hydrogen gas is to be produced fromstream 20. For example, when region 34 produces hydrogen by steamreforming, it will contain one or more reforming catalyst beds 82 inwhich the feed stream is at least substantially converted into hydrogengas and carbon dioxide. A byproduct of this reaction is carbon monoxide,which in concentrations of even a few parts per million may permanentlydamage a PEM fuel cell stack. When the feedstock is methanol, theprimary reaction is

CH₃OH+H₂O=3H₂+CO₂

As discussed, the reaction in hydrogen-producing region 34 is typicallyconducted at elevated temperatures. For example, steam reforming ofmethanol is preferably conducted at a temperature above approximately250° C., and steam reforming of most other alcohols and hydrocarbons ispreferably conducted at temperatures above approximately 600° C. Toensure that region 34 is maintained above a determined minimumtemperature, and more preferably within determined temperature ranges,controller 28 monitors the temperature of region 34. In the context of asteam reformer and other temperature-dependent catalyzed reactions, itis preferable that controller 28 monitors the temperature of thecatalyst bed at one or more locations within or adjacent the catalystbed to ensure that the bed is within determined temperature ranges.Should the temperature be approaching or below a determined thresholdvalue, controller 28 may cause the temperature to be raised, such as bysending additional fuel to combustion region 60. Controller 28 may alsomonitor the pressure in region 34, via a suitable pressure sensor orpressure regulator, to maintain the pressure in the region withinselected limits.

It is within the scope of the present invention that controller 28 maybe adapted to direct more than one type of command signal responsive todetected values of an operating variable. For example, controller 28 maybe programmed to automatically try to achieve and maintain, via commandsignals, a determined value of an operating parameter, such as thetemperature in hydrogen-producing region 34, the pressure in separationregion 38, etc. This level of automation may be referred to as a firstlevel of control, in which the controller maintains a particularoperating parameter at or near a desired value. Typically, this valuewill be bounded by threshold values that establish determined minimumand/or maximum values. Should the measured value of the operatingparameter approach or exceed one of the threshold values, controller 28may send command signals other than those used in the first level ofcontrol described above. For example, the controller may execute itsshutdown subroutine to transition the fuel processing system to its idleor off operating state.

When the performance of the mechanism utilized in the hydrogen-producingregion is temperature dependent, processor 16 will typically include amechanism for selectively heating the hydrogen-producing device. Thereforming catalyst bed described above is an example of such atemperature-dependent mechanism. For example, it is preferable that bed82 be preheated to at least 250° C. when steam reforming methanol, andat least 600° C. when steam reforming other alcohols and hydrocarbons.

An example of a suitable mechanism for heating the reforming catalyst,or any other hydrogen-producing device requiring an elevatedtemperature, is a preheating assembly 90, such as shown in FIG. 5. Asshown, assembly 90 includes a pump assembly 92 that draws a fuel stream94 from a fuel supply 96 and combusts this stream to heat bed 82 orother hydrogen-producing device, as schematically illustrated in dashedlines at 100. Supply 96 may be located external fuel processing assembly12. When fuel supply 96 is adapted to deliver a compressed gaseous fuel,pump assembly 92 is not required, and the fuel stream may be delivereddirectly to an igniter 98, such as schematically illustrated at 101.Igniter 98 is shown in FIG. 5 and is meant to include any suitablemechanism for igniting fuel stream 94. This includes a glow plug orresistance element, spark plug, pilot light, or other suitable hotsurface, flame or spark to ignite the fuel. Another example of asuitable igniter 98 is a combustion catalyst.

Preheating assembly 90 may utilize any suitable fuel. Examples ofsuitable fuels include propane, natural gas, and transportation fuels.Another example of a suitable fuel is hydrogen gas, such as hydrogen gaspreviously produced by fuel processor 16. In fact, controller 28 maydirect a portion of the product hydrogen stream to be recycled topreheating assembly 90 through a suitable conduit (not shown) when thetemperature in the hydrogen-producing region approaches or falls below adesired minimum temperature. When the byproduct stream containssufficient hydrogen gas or other combustible material, it too may serveas a fuel source for preheating assembly 90 or combustion region 60.

As shown, controller 28 communicates with fuel supply 96 and pumpassembly 92, such as previously described in connection with feedstocksupply 78 and pump assembly 70. Controller 28 also communicates withigniter 98. This communication is preferably two-way communication sothat controller 28 can not only selectively activate and deactivate theigniter, but also monitor the igniter to detect a lack of ignition, suchas within a determined time period after a control signal is sent toactivate the igniter, or an unintentional flameout. In either situation,the controller may trigger the shutdown subroutine. Controller 28 may,for example, automatically attempt to reactuate the igniter, and thentrigger the shutdown subroutine should the relight attempt fail.Preferably, actuating the shutdown subroutine also causes controller 28to send a command signal to stop pump assembly 92 and the flow of fuelfrom supply 96.

Another embodiment of a preheating assembly is shown in FIG. 6 andgenerally indicated at 102. Instead of providing heat tohydrogen-producing region 34 through the use of a combustible fuel,assembly 102 utilizes a heater 104, such as a resistance heater thatreceives an electric current from a power source 106. Examples of powersource 106 include fuel cell stack 14, a battery bank storing currentfrom fuel cell stack 14, an external source of electric current, and abattery bank independent of fuel cell stack 14. Controller 28 sendscontrol signals to heater 104 to selectively activate, deactivate andcontrol the heat output of the heater, responsive to inputs from sensorsin region 34 and/or preprogrammed commands stored in controller 28.

Heating, such as in the above preheating assemblies or in thesubsequently described combustion region, may also be accomplishedthrough the use of an external heat source. An example of this isthrough heat exchange with the combustion output from an externalcombustion source. Another example is through heat exchange with anoutput stream from a boiler or furnace.

Resultant stream 36 from region 34 is passed to separation region 38, asshown in FIG. 7. In region 38, stream 36 is divided into product stream40 and byproduct stream 42. One suitable method for partitioning stream36 is through the use of a hydrogen-selective membrane, which preferablyisolates at least a substantial portion of the hydrogen gas, whilelimiting or preventing the inclusion of undesirable compositions. InFIG. 7 a membrane assembly 84 is shown and includes at least onehydrogen-selective membrane 86. Examples of suitable membranes aremembranes formed from palladium or palladium alloys. Other suitablehydrogen-separation devices that may be used include absorbent beds,catalytic reactors, and selective oxidation. Examples of suitableabsorbent beds include zeolite and carbon beds, and an example of asuitable catalytic reactor includes a water-gas-shift reactor.

As shown, controller 28 communicates with separation region 38 tomonitor such process parameters as the temperature and/or pressurewithin membrane assembly 84 or any other hydrogen-separation devicebeing used therein. Controller 28 may also monitor the temperatureand/or pressure of product and byproduct streams 40 and 42. Inmembrane-based separation systems, the flow of hydrogen gas through themembrane is typically driven by maintaining a pressure differentialbetween the opposed sides of the membrane(s). Therefore, controller 28may monitor and regulate this pressure responsive to the inputs fromsensors on both sides of the membrane. Examples of suitable pressuresare a pressure of approximately 30 psig or more on thehydrogen-production side of the membrane and a pressure of approximately5 psig or less on the product side of the membrane. However, thepressure on the product side of the membrane(s) may be greater than 5psig if the pressure on the hydrogen-producing side of the membrane(s)is sufficiently elevated. Preferably, the product side of the membraneis maintained as close to ambient pressure as possible, while beingmaintained above the minimum determined pressure for the fuel cell stackor other end destination for the product stream. These desired thresholdvalues, similar to the other controlled thresholds discussed herein, arestored by controller 28, such as in a memory device 88, and morepreferably in a nonvolatile portion of a memory device. Memory device 88is shown schematically in FIG. 8 only, but it should be understood thatdevice 88 may be included with any embodiment of control system 26described herein.

In some embodiments of fuel processor 16, product stream 40 may stillcontain more than an acceptable concentration of some compositions.Therefore, it may be desirable for fuel processor 16 to include apolishing region 44, such as shown in FIG. 8. Polishing region 44includes any suitable structure for removing or reducing theconcentration of selected compositions in stream 40. For example, whenthe product stream is intended for use in a PEM fuel cell stack or otherdevice that will be damaged if the stream contains more than determinedconcentrations of carbon monoxide or carbon dioxide, it may be desirableto include at least one methanation catalyst bed 110. Bed 110 convertscarbon monoxide and carbon dioxide into methane and water, both of whichwill not damage a PEM fuel cell stack. Polishing region 44 may alsoinclude another hydrogen-producing device 112, such as another reformingcatalyst bed, to convert any unreacted feedstock into hydrogen gas. Insuch an embodiment, it is preferable that the second reforming catalystbed is upstream from the methanation catalyst bed so as not toreintroduce carbon dioxide or carbon monoxide downstream of themethanation catalyst bed.

The product hydrogen stream, now generally indicated at 46, is nextpassed to an output assembly 50 and thereafter expelled from the fuelprocessor. As shown in FIG. 8, output assembly 50 includes a valveassembly 114 including one or more valves that are controlled responsiveto command signals from controller 28. It should be understood thatvalve assembly 114 may include a single valve adapted to distribute theflow between two or more output streams, or it may include a pluralityof valves, each directing flow into a different output stream. Forexample, streams 52 and 54 are shown in FIG. 8 adapted to deliver aselected portion of product stream 46 to fuel cell stack 14 and storagedevice 56. Each stream may contain anywhere from 0-100% of stream 46,depending upon the control signals sent by controller 28. For example,if there is suitable electrical or thermal load being applied to stack14 by an associated device, such as device 22, then all of the productstream may be sent to the fuel cell stack. On the other hand, if thereis insufficient load being applied to stack 14 to require the entiretyof stream 46, then some or all of the stream may be otherwise disposedof, such as being sent to storage device 56. It should be understoodthat processor 16 may include additional conduits providing additionaldestinations for product hydrogen stream 46. For example, a selectedportion of the stream may be sent to combustion region 60 or preheatingassembly 90 to be used as a fuel source, or it may be transported to ahydrogen-consuming device other than stack 14 or device 56.

Output assembly 50 preferably includes a vent stream 55 through whichvalve assembly 114 may selectively send some or all of the hydrogenstream, responsive to control signals from controller 28. For example,during startup and shutdown sequences of the fuel processor, when theproduced hydrogen stream may contain impurities or for other reasons beundesirable as a feed to stack 14, vent stream 55 may be used to disposeof any flow delivered to the output assembly. Stream 55 may exhaust thestream to the atmosphere, deliver the stream to a combustion unit, ordispose of the stream in any other suitable manner. Controller 28 mayalso direct, via command signs to valve assembly 114, all flow to stream55 during the idle, or standby, operating states of the fuel processor,where only minimal flow is typically received and when no hydrogen gasis demanded by stack 14.

As shown in FIG. 8, controller 28 not only directs the operation ofvalve assembly 114, but also receives inputs indicative of suchparameters as the pressure, temperature and/or flowrate in streams 52,54 and 55. These inputs may be used, for example, to ensure that valveassembly 114 is operating properly and to regulate the pressure instream 52 going to fuel cell stack 14 to ensure that the pressure is notlower than a determined minimum pressure. In systems where it ispreferable that the pressure of stream 52 be as low as possible,controller 28 may also selectively control a pressure regulator toreduce the pressure if it is above a determined value.

In FIG. 8, dashed communication pathways 62′ are shown to demonstrateschematically that control system 26 may also enable one- or two-waycommunication between controller 28 and fuel cell stack 14, storagedevice 56 or any other destination for the product hydrogen streams. Forexample, responsive to inputs representative of the load being appliedto stack 14 from device 22, controller 28 may regulate the rate at whichhydrogen is sent to stack 14. Responsive to this input from stack 14,controller 28 may also regulate the rate at which hydrogen gas isproduced by processor 16 by controlling the rate at which feedstock isdelivered to the fuel processor by the feed assembly. For example, ifthere is little or no load being applied to stack 14 and system 10 isnot adapted to store or otherwise utilize hydrogen gas, then controller28 may automatically regulate the rate of hydrogen production responsiveto the applied load.

In FIG. 9, an embodiment of combustion region 60 is shown in moredetail. As shown, region 60 includes a pump assembly 120 that includesat least one pump adapted to draw a stream 122 of a combustible fuelfrom a supply 124. Combustion fuel supply 124 may be a compressedgaseous fuel, in which case pump assembly 120 is not required. Similarto the above-described preheating assembly 90, any suitable igniter 126may be used to ignite the fuel and thereby generate heat to maintain thefuel processor within determined temperature ranges. Responsive toinputs, such as from a temperature sensor in hydrogen-producing region34, controller 28 regulates the rate at which fuel is drawn from supply124 to thereby control the temperature of the processor. The examples ofigniters and suitable fuels discussed above with respect to preheatingassembly 90 are also applicable to combustion region 60, as well as theoperating parameters that may be monitored and selectively regulated bycontrol system 26.

Although the operation of the fuel processing system is preferably atleast substantially automated by control system 26, it may still bedesirable for the fuel processing system to include a user interface,such as interface 58 shown in FIG. 10. Interface 58 includes a displayregion 130 through which information is conveyed to the user bycontroller 28. Typically, the displayed information is indicative of theoperating state of the fuel processor, as will be described in moredetail subsequently. Also, if the controller detects a malfunction andactuates the shutdown subroutine, display region 130 may include anotification of the fault, including the detected malfunction. Themessages or other information displayed to the user are typically storedin the controller's nonvolatile portion of its memory device 88, and areautomatically displayed by controller 28 responsive to triggering eventsdetected by the control system. Display region 130 may also includedisplays of operating parameters detected by the control system, such asselected flowrates, temperatures and pressures, supply levels, etc.

As shown in FIG. 10, interface 58 may also include a user input device132 through which a user may send commands to the controller. Forexample, the user may manually input commands to cause controller 28 tostartup the fuel processor, shutdown the fuel processor, immediatelystop operation of the fuel processor, transition to an idle, or standby,state, etc.

It is within the scope of the present invention that input device 132may be used to change the determined values utilized by controller 28 todetermine whether the current operating state of the fuel processorneeds to be adjusted. However, it may be desirable for some or all ofthe determined values to be protected from being changed by a user, orat least prevented from being changed by an unauthorized user, such asone that does not previously enter a passcode or other authorizingcommand to the controller.

A user alert device 134 is also shown in FIG. 10 and may be used tosignal to a user that a malfunction or fault condition is detected.Device 134 may include any suitable mechanism for attracting a user'sattention, such as by emitting visual or audible signals. Also shown inFIG. 10 is a reset 136, which enables a user to cause the controller torestart the fuel processing system, such as after a fault is detected.

As discussed, control system 28 automates the operation of fuelprocessing assembly 12, and preferably automates the operation of theentire fuel processing system. In the preceding discussion, illustrativecomponents, or regions of fuel processors and fuel processing systemsaccording to the present invention were described. Also discussed werethe interaction of control system 26 with these components, includingexamples of the operating parameters that may be monitored by controller28, as well as the control signals that controller 28 may use toregulate the operation of the fuel processing system. It should beunderstood that any desired threshold values may be used. For example,controller 28 may be programmed to utilize the specific operatingparameters required for the feedstock, hydrogen-producing mechanism,separation mechanism and product-stream destination implemented in aparticular embodiment of the fuel processing system. As a specificexample, control system 26 may be programmed to automate fuel processingsystem 10 according to any or all of the values of operating parametersdescribed in U.S. Pat. No. 6,376,113. Of course, other values may beused as well.

Controller 28 preferably is programmed to automatically switch betweenand maintain defined operating states according to preprogrammedsubroutines responsive to user inputs (such as to startup or shutdownthe fuel processing system) and/or inputs from the operating parameters(such as the detection of a malfunction or operating parameter exceedinga defined threshold value for which automated correction is noteffective or preprogrammed).

To illustrate how control system 26 may automate the operation of a fuelprocessing assembly and/or system, the following discussion and FIGS. 11and 12 are provided. In FIG. 11, examples of possible operating statesand the relationships therebetween are schematically illustrated. As thefollowing discussion demonstrates, the operating states may be achievedwith only a few command signals from the controller 28 since most of thefuel processing system is a passive system that requires an input streamto trigger a result. For example, once hydrogen-producing region 34reaches at least a minimum acceptable operating temperature, itautomatically produces hydrogen gas when feed stream 20 is deliveredthereto. Similarly, separation region 38 and polishing region 44automatically separate and polish, respectively, any stream deliveredthereto, and fuel cell stack 14 automatically produces an electriccurrent when a hydrogen stream is delivered thereto.

In FIG. 11, four illustrative operating states are shown, namely, offstate 140, running state 142, standby state 144, and faulted state 146.Off state 140 corresponds to when there is no feedstock being deliveredto fuel processor 16, no heat being generated in combustion region 60 orpreheating assembly 90, and the fuel processor is depressurized. Thefuel processing system is not operating and has no input or outputstreams.

Running state 142 corresponds to the state where the fuel processor isreceiving a flow of feedstock and producing hydrogen therefrom. Theproduct hydrogen stream is expelled from output assembly 50 and sent tofuel cell stack 14 or another destination. In the running state,combustion region 60 typically will also be used either intermittentlyor continuously to maintain the temperature with the fuel processorwithin determined threshold values, and preferably at or near a selectedoperating value between these threshold values.

Standby state 144 corresponds to when the fuel processor istransitioning between its off and running states. In this state, thecontroller achieves and maintains determined operating temperatures andpressures within the fuel processor, but typically little, if any,product stream will be delivered to fuel cell stack 14 or storage device56. Instead, any product stream reaching output assembly 50 willtypically be combusted for heat, exhausted as waste gas, or otherwisedisposed of. Standby state 144 may also be thought of as an idle statebecause the fuel processing system is primed to produce hydrogen and/orelectric current, but none is required or being generated in more than anominal amount, such as would be required to operate the fuel processingsystem.

From off state 140, controller 28 automatically directs the fuelprocessor to achieve its standby operating state responsive to an inputsignal, such as a user input from interface 58, a load being applied tofuel cell stack 14, a timed input signal from controller 28 itself, etc.If standby state 144 is successfully achieved, controller 28 may eitherbe programmed to direct system 10 to attain its running state, namely,by starting the flow of feedstock to fuel processor 16, or to await theinput of a signal to trigger the transition to running state 142.

In either running state 142 or standby state 144, the detection of amalfunction will cause controller 28 to automatically transition tofaulted state 146. Faulted state 146 corresponds to when the controllerdetects a malfunction, such as an operating parameter exceeding adetermined threshold value. When this occurs, the controller preferablyactuates user alert 134 to notify the user that there is a problemdetected in the fuel processing system. Controller 28 also stops theflows of fuel and feedstock within the system, such as by directing thepump assemblies to stop drawing from their corresponding supplies.Similarly, controller 28 may direct any product stream within the fuelprocessor to be utilized through stream 55, thereby preventing anypotentially contaminated stream from reaching fuel cell stack 14 orstorage device 56. The igniters may also be deactivated.

From faulted state 146, the controller will either direct the transitionto off state 140, such as if no reset signal is received, or willattempt to transition back to standby state 144. If an input directingthe controller to shutdown the fuel processing system is received whilein the running state, controller 28 will preferably transition first tothe standby state to safely stop the production of hydrogen, and then tothe off state.

It should be understood that controller 28 may be programmed to includeother operating states than those shown in FIG. 11. For example, theremay be more than one running state, such as to correspond to differentrates of hydrogen production. Similarly, there may be separate startupand standby operating states.

Controller 28 transitions between the operating states by executingvarious programmed subroutines, each of which directs the controller toautomatically send input signals required to achieve a selected result.Illustrative examples of suitable subroutines are shown in FIG. 12 andinclude preheat 150, pressurize 152, standby 154, online 156 andshutdown 158 and off 160.

In preheat subroutine 150, controller 28 sends command signals requiredto begin heating the fuel processor to its desired operating temperaturerange. Typically, this subroutine includes directing combustion region60 to begin heating the fuel processor. It may also include directingpreheating assembly 90 or 102 to begin heating hydrogen-producing region34 to at least a minimum temperature required to effectively produce aproduct stream with an acceptable composition. Both of theseheat-producing units will typically continue to be used during thesubsequent pressurize subroutine 152, then the preheating assembly willgenerally be deactivated (by turning off the igniter and/or stopping theflow of fuel, or by deactivating the heater). The combustion region willtypically continue to operate during all but the shutdown and offsubroutines, although the relative rate of operation may be regulated bycontroller 28, such as by controlling the rate at which fuel isdelivered to the igniter.

Once the hydrogen-producing region has achieved a selected thresholdtemperature, which is monitored and detected by a sensor assembly incommunication with controller 28, controller 28 executes pressurizesubroutine 152. In pressurize subroutine 152, feed stream 20 isintroduced into the fuel processor (by controller 28 actuating pumpassembly 70) to begin the production of hydrogen and thereby pressurizethe fuel processor. Once the fuel processor reaches a selected operatingpressure, the controller executes standby subroutine 154. When standbysubroutine 154 is executed, controller 28 deactivates the preheatingassembly, and the controller regulates the flow of feed stream 20 toproduce a sufficient flow in product stream 52 and/or byproduct stream42 to provide fuel for combustion region 60.

When there is a demand for hydrogen product stream, such as when a loadis applied to fuel cell stack 14, the online subroutine is executed. Inthis subroutine, the controller increases the flow rate of feed stream20, thereby increasing the rate at which hydrogen is produced, and as aresult current is produced in stack 14. Valve assembly 114 is alsoactuated by a suitable command signal to direct hydrogen to fuel cellstack 14. Assembly 114 may optionally be actuated in the pressurizesubroutine to send a hydrogen stream to stack 14 so that stack 14 mayproduce current to power the operation of system 10.

Should a malfunction be detected by controller 28, controller 28 willautomatically execute its shutdown, or fault, subroutine. The shutdownsubroutine may also be executed responsive to a user input signal orprogrammed signal directing shutdown of the fuel processing system. Inthis subroutine, the controller stops the flow of feed stream 20, aswell as the flow of fuel to combustion region 60 and preheating assembly90.

If a command, such as the user actuating reset 136, is not received,controller 28 will next execute its off subroutine. In this subroutine,the controller deactivates any activated heater or igniter and beginsdepressurizing the fuel processor. Finally, when the fuel processingsystem is safely depressurized and all flows have stopped, the valves inassembly 114 are closed and the shutdown of the fuel processing systemis complete.

It should be understood that the above operating states and subroutineshave been presented to provide an example of how the invented controlsystem automates the operation of fuel processing system 10. Theexamples provided above should not be construed in a limiting sense, asmany variations of the subroutines, operating states and commandsexecuted therein are possible and are within the scope of the presentinvention. For example, when fuel processing system 10 includes astorage device 56 adapted to store a supply of hydrogen gas, this storedsupply may be sent to fuel cell stack 14 in the preheat subroutine toproduce current to power the operation of the fuel processing system.

The automation of fuel processing system 10 enables it to be used inhouseholds, vehicles and other commercial applications where the systemis used by individuals that are not trained in the operation of fuelprocessing systems. It also enables use in environments wheretechnicians, or even other individuals, are not normally present, suchas in microwave relay stations, unmanned transmitters or monitoringequipment, etc. Control system 26 also enables the fuel processingsystem to be implemented in commercial devices where it is impracticablefor an individual to be constantly monitoring the operation of thesystem. For example, implementation of fuel processing systems invehicles and boats requires that the user does not have to continuouslymonitor and be ready to adjust the operation of the fuel processingsystem. Instead, the user is able to rely upon the control system toregulate the operation of the fuel processing system, with the user onlyrequiring notification if the system encounters operating parametersand/or conditions outside of the control system's range of automatedresponses.

It should be understood that the above examples are meant to illustratepossible applications of such an automated fuel processing system,without precluding other applications or requiring that a fuelprocessing system according to the present invention necessarily beadapted to be used in all of the exemplary scenarios. Furthermore, inthe preceding paragraphs, control system 26 has been describedcontrolling various portions of the fuel processing assembly. It iswithin the scope of the present invention that the system may beimplemented without including every aspect of the control systemdescribed above. Similarly, system 26 may be adapted (i.e. programmed)to monitor operating parameters not discussed herein and may sendcommand signals other than those provided in the preceding examples.

While the invention has been disclosed in its preferred form, thespecific embodiments thereof as disclosed and illustrated herein are notto be considered in a limiting sense as numerous variations arepossible. Applicants regard the subject matter of the invention toinclude all novel and non-obvious combinations and subcombinations ofthe various elements, features, functions and/or properties disclosedherein. No single feature, function, element or property of thedisclosed embodiments is essential to all embodiments. The followingclaims define certain combinations and subcombinations that are regardedas novel and non-obvious. Other combinations and subcombinations offeatures, functions, elements and/or properties may be claimed throughamendment of the present claims or presentation of new claims in this ora related application. Such claims, whether they are broader, narroweror equal in scope to the original claims, are also regarded as includedwithin the subject matter of applicants' invention.

1. A method for controlling the operation of a hydrogen-producing fuelprocessing system, which system comprises a fuel processor which in usein a running state of the fuel processing system receives a feed streamand produces hydrogen gas therefrom, a feed assembly which in use in therunning state of the fuel processing system delivers the feed stream tothe fuel processor, a fuel cell stack which in use in the running stateof the fuel processing system receives at least a portion of thehydrogen gas, and control means which in use in the running state of thefuel processing system automates the operation of the fuel processingsystem, and in which method the control means: receives inputs ofselected operating parameters of the fuel processing system; determineswhether a measured value of a selected operating parameter is above orbelow a determined threshold value or value range and thereby outsidenormal operating parameters of the system, and, if so; selects inaccordance with said determination whether the fuel processing system isto be transitioned to a selected operating state available to the fuelprocessing system; and sends command signals to transition the fuelprocessing system from its running state to the selected state, whereinthe selected operating state is selected from a plurality of operatingstates that comprises at least: i) a standby state in which the controlmeans achieves and maintains determined operating temperatures andpressures within the fuel processor but in which hydrogen gas is notbeing generated in more than a nominal amount by the fuel processingsystem; and ii) a faulted state in which the flow of feedstock to thefuel processor is stopped and in which the control means awaits an inputfor a duration of time before automatically attempting to transition thesystem to another operating state of the plurality of operating states.2. The method of claim 1, in which the fuel processing system furthercomprises a hydrogen storage device which in use is adapted to store atleast a portion of the hydrogen gas produced by the fuel processor, andfurther in which, in the standby state, little if any hydrogen gas isdelivered to the fuel cell stack or the hydrogen storage device.
 3. Themethod of claim 1, wherein upon detection of a malfunction in therunning state, the control means automatically transitions the fuelprocessing system to the faulted state.
 4. The method of claim 3,wherein upon detection of a malfunction in the standby state, thecontrol means automatically transitions the fuel processing system tothe faulted state.
 5. The method of claim 1, wherein, in the runningstate, upon receipt by the control means of an input directing it toshutdown the fuel processing system, the control means is adapted todirect the fuel processing system to transition to the standby state andthen to an off state.
 6. The method of claim 1, wherein the selectedoperating parameters include one or more of the flow rate of fluid in afeed stream to the fuel processor, the temperature of a hydrogenproducing region of the fuel processor, and the pressure in the hydrogenproducing region.
 7. The method of claim 1, wherein the control meansautomatically transitions the fuel processing system from an off stateto the standby state responsive to an input signal.
 8. The method ofclaim 7, wherein the input signal is selected from a group consisting ofa user input, a load being applied to the fuel cell stack, and a timedinput from the control means.
 9. The method of claim 7, wherein, if thestandby state is successfully achieved, the control means directs thefuel processing system to attain the running state or to await the inputof a signal to transition the fuel processing system to the runningstate.
 10. The method of claim 1, wherein, from the faulted state, thecontrol means either directs a transition of the fuel processing systemto an off state if no reset signal is achieved, or attempts to direct atransition of the fuel processing system to the standby state.
 11. Themethod of claim 1, wherein, if an input directing the control means toshut down the fuel processing system is received while the fuelprocessing system is in the running state, the control means transitionsthe fuel processing system first to the standby state and then to theoff state.
 12. The method of claim 1, wherein the control meanscomprises a computerized controller which is included in an automatedcontrol system and the control system further comprises a sensorassembly which in use monitors the selected operating parameters of thefuel processor and the feed assembly and communicates inputs to thecontroller corresponding to the selected operating parameters, andwherein the controller transitions the fuel processing system betweenthe running state and the plurality of operating states based at leastin part on the inputs.
 13. The method of claim 12, wherein thecontroller utilizes a plurality of programmed subroutines to switch thefuel processing system between the plurality of operating states. 14.The method of claim 1, wherein the control means automatically shutsdown the fuel processing system if the value of a selected operatingparameter exceeds a corresponding threshold value.
 15. The method ofclaim 1, wherein the control means controls the operation of the fuelprocessing system to maintain the value of the selected operatingparameters at determined values or within ranges bounded by thresholdvalues.
 16. The method of claim 1, wherein in the standby state, thefuel processor is maintained at an operating temperature and anoperating pressure for producing hydrogen gas from the feed stream, butno more of the hydrogen gas is delivered to the fuel cell stack than isrequired to operate the fuel processing system in the standby state. 17.The method of claim 1, wherein in the standby state, none of thehydrogen gas is delivered to the fuel cell stack.
 18. The method ofclaim 1, wherein in the standby state, at least a substantial portion ofthe hydrogen gas is delivered to a heating assembly that is adapted tocombust the portion of the hydrogen gas to produce heat.
 19. The methodof claim 1, wherein the fuel processing system includes a user interfacein communication with the control means, which interface displaysinformation indicative of the performance of the fuel processing system.20. The method of claim 1, wherein the fuel processor includes a steamreformer.
 21. The method of claim 1, wherein the fuel cell stackincludes at least one proton exchange membrane fuel cell.